JP3046090B2 - Evaluation method for characteristic reliability of component materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating the reliability of characteristics of components of equipment such as an industrial plant, and more particularly to a method suitable for preparing guidelines for preventing phenomena such as stress corrosion cracking. The present invention relates to an evaluation method for equipment constituent materials.

[0002]

2. Description of the Related Art Conventionally, the specification of material strength required as a constituent material of an industrial plant, for example, a nuclear power plant, is based on ASME (American Societies).
etyof Mechanical Engineer
s) and the like, and if the plant is designed in accordance therewith, there will be no problem in strength and the plant will be highly reliable.

[0003]

However, there is not yet any specification for preventing environmental damage of component materials, particularly stress corrosion cracking. Also, whether or not the component materials of the plant used for 10 to 20 years or more have the possibility of stress corrosion cracking should be judged by a professional technician from the past cases of actual equipment. However, there is a problem that there is no analysis or determination method for completely predicting the stress corrosion cracking and preventing the stress corrosion cracking. In addition, stress corrosion cracking is a phenomenon that occurs only under severe conditions that combine the three factors of material, stress, and environment. In the past, to prevent this, we focused on each factor alone. All the time to make improvements.

[0004] For example, in the early 1950's, the piping system of a boiling water reactor used SUS304 steel with a high carbon content. Therefore, a chromium carbide is generated at a crystal grain boundary in a welded portion, and a chromium deficiency layer is generated near the grain boundary, a so-called sensitization phenomenon occurs. On the other hand, although the reactor water is high-purity water, it contains about 200 ppb of oxygen and is corrosive, so that stress-corrosion cracking occurs particularly in the heat-affected portion of the weld. There was a problem. For this, measures have been taken thereafter to use a low-carbon material that is difficult to sensitize. However, SUS30
Even if 4 steel is used, stress corrosion cracking does not occur in places where the stress is small. That is, if one of the three elements of the stress corrosion cracking is missing, the stress corrosion cracking problem does not occur.

The above three factors of stress corrosion cracking are examined in more detail. Considering the material factors, the difference between the case of stainless steel and the case of inconel material, that is, whether molybdenum or niobium is contained is considered. , Material factor 1
It can be seen that each case is made up of various influence factors. In addition, considering the environmental factors in more detail,
Oxygen concentration, temperature, hydrogen concentration, hydrogen peroxide concentration, conductivity,
It can be seen that it is made up of various influence factors such as gaps. Therefore, in order to compare the relative life of each part of the equipment and obtain a guideline for preferentially performing preventive maintenance on the shorter life, for example, the carbon content of the weld A is 0.06.
% SUS304 and the stress is 30 kg / mm ² , the welded part B has a carbon content of 0.04% SUS304.
304, the stress is 40 kg / mm ² , and if there is a gap, the welded portion C is further made of Inconel 600
And the stabilization parameter N [N = 0.13 (Nb + 2T
i) / C) Nb, Ti, and C are niobium, titanium, and carbon content% by weight] and the stress is 40 kg / mm.
^In the case of ² , when it is desired to determine which of these welds A, B, and C is the most urgent place to perform preventive maintenance, there is no evaluation technology conventionally, and the guideline and specifications are Because of this, it has never been possible to address this issue. As described above, in the conventional technology, there is no evaluation technology for analyzing the relationship between the degree of superimposition of the magnitude of various influential factors on the environmental damage of the component material and the life, and therefore, the stress corrosion cracking of the component material is prevented beforehand. It has the disadvantage that it cannot be done.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and expresses the relationship between the degree of superposition of the magnitude of various influential factors on the phenomena such as environmental damage of the component materials and the life of the components by an index. To provide a clear method for evaluating characteristics.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is based on the knowledge of the degree of various influencing factors on phenomena such as stress corrosion cracking of component materials such as stainless steel and inconel material, The present invention is directed to a method for evaluating the reliability of characteristics of an equipment material for evaluating the reliability of the equipment material for characteristics such as damage. Then, for each of the various influencing factors, focusing on one or more arbitrary influencing factors, keeping the degree of the other influencing factors constant, and setting the first factor between the magnitude of the focused influencing factor and the degree of the phenomenon. Find the function of. Next, the degree of criterion of the various influencing factors is determined, and a second function of the degree of the phenomenon when the various influencing factors take the reference value is obtained. Then, the ratio between the first function and the second function is calculated to obtain a function of the subdivision index of the affected factor of interest, and then the product of the function of the subdivision index of each of the affected factors is multiplied by a correction coefficient. And an index indicating the possibility that the above phenomenon can occur.

[0008]

According to the present invention, as described above, it is possible to quantitatively grasp the degree of the characteristic of each part of the component material. Therefore, it is possible to take measures against accidents such as damage at the design stage of a new plant and as preventive maintenance of an existing plant. The present invention is extremely effective especially when high reliability is required as in a nuclear reactor plant.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The process of the present invention comprises the following steps: (1) For each factor that affects the environmental damage of component materials, setting a relational expression between the size of the influential factor and the damage life. (2) Setting of standard life system. (3) Derivation of the subdivision index of the influential factor. (4) Derivation of an F-index at an arbitrary point on the device. It consists of four steps. Next, each of these steps will be described.

(1) For each of the factors that affect the environmental damage of the component materials, a relational expression between the size of the influential factor and the damage life is set. The relational expression between the magnitude of the influence factor i and the damage life may be based on experimental data or a theoretical expression based on a mechanism. FIG. 1 shows the relationship between the magnitude of the influence factor i and the damage life. t _i = g _i (X ==) (Equation 1) where t _i : life time g _i : function of influencing factor i X _i : size of influencing factor i To obtain this (Equation 1), Focusing on one or more specific influencing factors, setting other influencing factors under certain conditions (for example, acceleration conditions), changing the size of the influencing factors in various ways, and calculating the environmental damage life data of equipment components Get. Then, a relational expression between the focused influence factor and the life is obtained. Since the relational expression is obtained based on the data as described above, it is easy to understand the conclusion obtained from the actual F index. A theoretical formula based on the mechanism may be used,
It must be able to explain experimental data. Specific examples include a simple regression function or a polynomial regression curve when there are data points, a fitted curve of a theoretical equation by the parametric least squares method when there is data and theory, and a theoretical curve when there is no data. Use the formula. These functions are expressed as one of a Taylor expansion function, a function that can be approximated to the Taylor expansion, and a step function.

(2) Setting of reference life system Since the reference life system may be arbitrary, it may be a system of life data obtained in the laboratory or a system with damage cases. The magnitude of each of the influencing factors i constituting the reference life system is set, and the life time t _iR of the reference life system is obtained. FIG. 1 shows the relationship between the magnitude of the influence factor i and the lifetime t _iR . t _iR = g _iR (X _iR ) (Equation 2) where t _iR : life time of the reference life system g _iR : a function of the influence factor i X _iR : magnitude of the influence factor i constituting the reference life system Reference life system Is used as the life time of the reference life system when each influencing factor has a certain set value, but the idea is that the magnitude of each influencing factor in any part of each device is Is considered to be another value deviating from the magnitude of the influential factor, and a method of examining how many times the life of the reference life system due to this deviation is determined.

(3) Derivation of the subdivision index of the influential factor. The subdivision index F _i of the influential factor is defined by dividing (Equation 1) by (Equation 2), that is, the life ratio. FIG. 2 shows this relational expression. F _i = t _i / t _iR (Equation 3) = g _i (X _i ) / g _iR (X _iR ) (Equation 4) = F _i (X _i , X _iR ) (Equation 5) Meritsuto to relationship by obtaining the subdivided index F _i of the same influence factor i of many different systems, is that may be set having high reliability relational expression F _i. In this step, the subdivision index F _i of the influencing factor i is introduced. This is based on the influencing factor i under certain certain conditions (for example, acceleration conditions) and the above (Equation 1) and (Equation 1). 2), and the influence factor i
However, the subdivision index F _i can be similarly obtained under another certain condition (for example, acceleration condition). At this time, the subdivision index F _i obtained under each certain condition
Although but no problem when it is substantially the same, when the slightly different, more safety side selection subdivision index F _i, there is a room for introducing the correlation coefficient between factors that averaging or some conditions. That is, it is possible to check whether or not the subdivision index obtained by focusing on a certain influential factor has the same relationship even under a certain condition, and to bring in a correlation coefficient if the condition is different.

(4) Derivation of an F-index at an arbitrary point on the device The F-index at an arbitrary point on the device is represented by the product of the subdivision indices of all the influence factors acting on the point. FIG. 3 shows a relational expression (Equation 6) of the F index. In this relational expression, X _i
When X = X _iR , F = 1. Thus, knowing the X _i for each part of each device can be calculated F index. As described above, the F index at an arbitrary position of the device means that it is the product of the subdivision indices of all the influence factors acting on the position. This will be described with reference to FIG. FIG. 5 shows the relationship between the effect of stress on the stress corrosion cracking life of stainless steel SUS304 and the amount of carbon in the material (however, other factors affecting the stress corrosion cracking of stainless steel were the same). . Then, the reference stress (here, design stress Sy
Is 1.54, and the carbon content in the material is 0.06 wt%. The life point at this time is assumed to be a. On the other hand, when the stress ratio of the portion where the F index is to be obtained is 1.10 and the carbon content is 0.04 wt%, first, the stress is not changed from the point a, and the carbon content is 0.04 wt%. Then, point b is reached. Thus, F ₁ can be known from the subdivision index of the carbon content. Next, from the stress subdivision index F ₅ =, when the stress ratio becomes 1.10, c
Points are found. Accordingly, F ₁ = t ₁ (0.04, 1.54) / t _R (0.06, 1.54) (Equation 7) F ₅ = t ₅ (0.04, 1.10) / t ₁ ( 0.04, 1.54) (Equation 8) ΔF = F ₁ × F ₅ = t ₅ (0.04, 1.10) / t _R (0.06, 1.54) (Equation 9) It is the product of each subdivision index. The larger the F index is, the longer the reference life is from the reference life, and therefore, it can be determined that the position has high reliability.

FIG. 6 shows the relationship between the stress ratio of the Inconel material and the amount of carbon in the material (however, other stress corrosion cracking influencing factors of the Inconel material were the same). , F index can be represented by the product of the subdivision indices of the influential factors. F ₂ = t ₂ (N, 1.54) / t _R (0.06, 1.54) (Equation 10) F ₅ = t ₅ (N, 1.10) / t ₂ (N, 1.54) (Equation 11) F ₇ = t ₇ (N, 1.10, gap) / t ₅ (N, 1.10) (Equation 12) ∴F = F ₂ × F ₅ × F ₇ = t ₇ (N, 1 .10, gap) / t _R (0.06, 1.54) (Equation 13)

Next, with reference to FIGS. 7, 8 and 9, a flow for calculating the F index of the heat affected zone in the welded portion of the stainless steel SUS304 will be described. (1) Subdivision index F ₁ of carbon content (see FIG. 7) F ₁ = g ₁ (C, 0.06) (Equation 14) = exp {ln10 (ΣAiC ¹ )} (Equation 15) where Ai: coefficient C: carbon amount (wt%) 0.06: carbon amount of the reference system (wt%) When C = 0.06, F ₁ = 1.

(2) Subdivision index F _{3 for} sensitization at low temperature (FIG. 7)
(See Reference) The phenomenon of sensitization of component materials according to the operating temperature is called low temperature sensitization (LTS). calculating a subdivided index F _3. F ₃ = g ₃ (LTS, none) (Equation 16) = α ₁ (Equation 17) where LTS: Variable of low-temperature sensitization None: No LTS of reference system α ₁ : Constant when given set life is given Value.

(3) Subdivision index F _{4 for} stress relief annealing
(See FIG. 7) In the stress relief annealing, a material is heat-treated at a constant temperature for a predetermined time. Therefore, when the carbon content in the material is high, the sensitization phenomenon of the material may be promoted. Although the subdivision index can be configured using the heating temperature and the heating time as parameters, the heating temperature and the heating time are not so different in practice, so the presence or absence of stress relief annealing was used as a parameter here. F ₄ = g ₄ (SR, None) (Equation 18) = α ₂ (Equation 19) Here, when there is no SR parameter (parameter of stress relief annealing), F ₄ = 1, and when there is an SR parameter, F ₄ = α ₂ .

(4) Stress subdivision index F ₅ (FIG. 8, FIG. 1)
1) The subdivision index of the stress of the stainless steel SUS304 can be obtained as follows. The effect of stress on the stress corrosion cracking life is shown in FIG. 10, which is formulated as shown in FIG. The maximum stress ratio S is obtained by dividing the stress by the design stress Sy. Minimum stress ratio (Sm
in ₀ ) is 1 when the SCC is a film breaking mechanism. The safety factor μ is obtained by multiplying the minimum stress ratio (Smin ₀ ) by a coefficient, and a value of 1 or less and 0 or more is substituted. Coefficient α
₀ is a quantity related to the inclination of the center of the curve in FIG. The reference stress ratio S _R is the stress ratio of the reference life system.

(5) Subdivision index F _{6 of} environmental effects (see FIG. 9) As an environmental effect, the subdivision index F ₆ of oxygen is data of the effect of the amount of oxygen on the stress corrosion cracking life as in the other cases. Can be derived from F ₆ = g ₆ When (DO, DO _R) (Equation 20) = exp [ln10ΣBi {log 10 (DO)} 1] ( Equation 21) where the DO = 200 ppb, a F ₆ = 1.

(6) Subdivision index F _{7 of the} gap (see FIG. 9) The presence of the gap shortens the stress corrosion cracking life of the material. Accordingly Like other subdivided index, representing the subdivided index F ₇ clearances as follows. F ₇ = g ₇ (gap, none) (Equation 22) = α ₃ (Equation 23)

(7) Accordingly, the F index of stainless steel (see FIG. 9) is represented by F = F ₁ × F ₃ × F ₄ × F ₅ × F ₆ × F ₇ (Equation 24).

FIGS. 12, 13 and 14 are flow charts for calculating the subdivision index F of the heat-affected zone in the welded portion of the Inconel material. Of subdivided index F, subdivided index F ₄ stress relief annealing, subdivided index F ₅ stress, subdivided index F ₆ and gap subdivided index F ₇ environmental effects
Are the same as those of the stainless steel shown in FIGS. 7 to 9, and the description thereof is omitted here. F ₂ and F ₃ of the subdivided index F is subdivided index F no stainless steel from the feature that it is Inconel material. Inconel materials have different stress corrosion resistance depending on the value of the stabilization parameter N. The stabilization parameter N is as follows: N = 0.13 (Nb + 2Ti / C) (Equation 25) Here, Nb, Ti, and C are the content wt% of each in the material. Subdivided index F ₂ are those determined connexion by the heat treatment and the stabilization parameters N. It is considered that the state is as-welded (AW), the state of stress relief annealing (SR) after welding, or simply the state of stress relief annealing (SR) alone. When the object is AW, the subdivision index F ₂ is as follows. F ₂ = β ₁ (N <8) (Equation 26) F ₂ = β ₂ (N ≧ 8) (Equation 27) On the other hand, in the case of SR, the subdivision index F ₂ is assumed to be as follows. _{F 2 = β 3 (N <} 12) ( Formula _{28) F 2 = β 4 (} N ≧ 12) ( Equation 29) In other words, subdivided index F ₂ as shown in FIG. 15 and FIG. 16 is a stable parameter N This is a step function that changes with the time.

On the other hand, the subdivision index F ₃ indicates what happens when low temperature sensitization (LTS) is further added. In the absence of low-temperature sensitization (LTS), the refining index F ₃ is already calculated for the case with the stabilization parameter N and the presence or absence of stress relief annealing (SR) in the refining index F ₂ . When there is low temperature sensitization (LTS), it is considered separately whether low temperature sensitization (LTS) is performed after welding or low temperature sensitization (LTS) is performed after removal annealing (SR).

When the object is welded (AW), the subdivision index F ₃ is as follows. F ₃ = β ₅ (N <8) (Equation 30) F ₃ = 1 (N ≧ 8) (Equation 31) Here, when N ≧ 8, the subdivision index F ₃ becomes 1
When it comes to the SCC resistance condition material, it does not deteriorate even when a slight heat effect such as low temperature sensitization (LTS) is applied.

When the object has undergone stress relief annealing (SR), the subdivision index F ₃ is as follows: F ₃ = β ₆ (N <12) (Equation 32) F ₃ = 1 (N ≧ 12) (Equation 33) Here, when N ≧ 12, the subdivision index F ₃ becomes 1 because of the SCC resistance. When used as a condition material, low-temperature sensitization (LT
This means that the SCC resistance does not deteriorate even when a slight thermal influence such as S) is applied.

Next, an example in which actual data is applied will be described below. FIG. 17 is a diagram showing the results of a stress corrosion cracking test performed on a test piece of a SUS304 steel welded joint in high-temperature pure water at 288 ° C. and an oxygen content of 8 ppm. Note that the stress was 2.5 Sm (Sm: design stress) as a stress corrosion cracking test condition, and a gap was provided in the test piece. The circles in the figure indicate stress corrosion cracking (SC
Those without C) and those with a black circle indicate those where stress corrosion cracking (SCC) occurred in the heat affected zone. As shown in the figure, when a large number of the same test pieces are tested at the same time, the rupture life of the test pieces varies.

FIG. 18 shows the life analysis of the stress corrosion cracking test data. The following equation is applied to the life analysis. −dN / dt = kN (Equation 34) ∴ln (N ₀ / N) = k (t−t ₀ ) (Equation 35) where N ₀ : initial number of test pieces N: sound at time t, ie, stress Number of test pieces not corroded by corrosion cracking k: stress corrosion cracking reaction constant t: time t ₀ : start time of stress corrosion cracking From the results in FIG. 18, the life system of stress corrosion cracking in FIG. It can be characterized that (t ₀ ) is 13.3 hours. As described above, for one stress corrosion cracking life system, the degree of the stress corrosion cracking influencing factors constituting the stress corrosion cracking life system, that is, the F index and the stress corrosion cracking initiation time (t ₀ ) which is the life parameter of the stress corrosion cracking. A set of data can be obtained. Such a set of data can be obtained for various life systems.

FIG. 19 is a plot of the data of the F index and the stress corrosion cracking (SCC) start time (t ₀ ) obtained as described above for various life systems. The data points 1 to 5 shown in the figure have the following sources. That is, data points 1 to 3 are data obtained by analyzing the actual test results of the stainless steel pipe welded joints (the Nuclear Engineering Center: the current state of the nuclear power generation facility reliability verification test, 1984) by the above method. Data point 4 is EPRI-WS-1
74, Vol. 1 (1980). Further, data point 5 is
ionic Corrosion Forum No.
86-253, p. 9 (1986).

In the figure, a small F-index means that the conditions for accelerating the stress corrosion cracking are large, that is, the degree of superposition of the stress corrosion cracking is large. (T ₀ ) also becomes shorter. vice versa,
A large F index means that the conditions for accelerating stress corrosion cracking are small, that is, the degree of superposition of stress corrosion cracking is small, and therefore, it is difficult to cause stress corrosion cracking and the life is extended. Therefore, the data in FIG. 19 clearly shows that there is a correlation between the F index and the stress corrosion cracking life.

Referring to FIG. 19, an example of evaluating the reliability of a device for stress corrosion cracking at an arbitrary position will be described below. The relational expression between the F index and the stress corrosion crack initiation time (t ₀ ) is obtained for the data band shown in FIG. F = h (t ₀ ) (Formula 36) For example, the lower limit (lnF) of the data band is represented by the following formula as an example. lnF = Alnt ₀ + B (Equation 37)

On the other hand, assuming that the reliability target for stress corrosion cracking of the equipment material is t _T (h), the following relationship must be satisfied. InF _T > Alnt _T + B (Equation 38) where A: coefficient B: constant t _T : target time for ensuring reliability at the target part of the device F _T : F index required to achieve t _T Note that FIG. It is also possible to calculate the above-mentioned F _T by performing statistical processing on the data band shown in FIG. _{∴F T> h (t T,} γ) ( Equation 39) On the other hand, for each evaluation target portion of the instrument material, and calculates the F index, when the value and Fx, when Fx is less than F _T, its position is It is determined that stress corrosion cracking will occur during the target use time of the equipment. Therefore, measures should be taken so that the F value becomes larger than F _T for at least one or more of the various influencing factors affecting the stress corrosion cracking. For example, it is necessary to reduce stress, particularly residual stress, and to reduce oxygen concentration in high-temperature water. Also,
If there is a possibility that the F value may decrease due to the control of environmental conditions or the change over time of the material or stress, follow the change over time or predict the change so that the F value becomes higher than the target F value in advance. In addition, control of the stress corrosion cracking factor should be performed.

Further, in the present invention, when multiplying the product of the functions of the subdivision indices of the influencing factors by a correction coefficient to obtain an index indicating the possibility that a phenomenon may occur, the degree of the influencing factor is given by the Monte Carlo method. Thus, the frequency distribution in which the phenomenon can occur can be obtained by substituting the correction coefficient into the correction coefficient. In other words, the magnitude of the influencing factor in the above-described embodiment forms the F-index formula using the representative value of the average value. However, if the distribution (frequency distribution) of the magnitude of each influencing factor is known, the F index is used. The purpose of the present invention is to evaluate the reliability of the characteristics of component materials using the Monte Carlo method in the formula of the index. The Monte Carlo method itself is generally known, and if one example is briefly described, if there are 100 target portions, a random number is generated 100 times for each influencing factor to obtain an F value, and the distribution of the F value is obtained. , The characteristic reliability of the component material can be evaluated.

In the present invention, the first function is represented by any one of a function of Taylor expansion, a function that can be approximated to Taylor expansion, and a step function, and t _i = g _i (X _i ) (Equation 40) A function of the degree of the phenomenon when the influencing factor takes the reference value is obtained, and t _iR = g _iR (X _iR ) (Equation 41) The ratio of these functions is obtained, and as a function of the subdivision index of the focused influencing factor, _i = g _i (X _i ) / g _iR (X _iR ) (Equation 42) = F _i (X _i , X _iR ) (Equation 43) Can be obtained by Taylor expansion, and the two can be multiplied to obtain the value as an index indicating the possibility that the phenomenon can occur.

Furthermore, in the present invention, each influential factor n
For each of the influential factors, focus on at least one or more m influential factors that are different from any of the influential factors, and keep the degree of the other influential factors constant. , And expressed as one of a Taylor expansion, a function that can be approximated to the Taylor expansion, and a step function for each of the influencing factor variables of each of the influencing factors, and t _ij ... _k = f _ij ... _k (X _i , X _j ..., X _k ) (Equation 44) Next, the reference level of each influencing factor is determined, and a function value of the degree of the phenomenon when each influencing factor takes a reference value is obtained. T _ij ... _KR = f _ij ... _kR (X _iR , X _jR ..., X _kR ) (Equation 45) The ratio F of these two functions is obtained. _{F ij ... k = t ij ...} kR / t ij ... kR = f ij ... k (X i, X j ..., X k) / f ij ... kR (X iR, X iR ..., X kR) = F ij ... _{k (X i, X j,} ..., X iR, X jR ..., X kR) ( equation 46)

Further, a correction coefficient, which is a function of the influencing factor, is obtained by Taylor expansion of the product of the functions of the subdivision indices of the influencing factors, and the two are multiplied to obtain the logarithm as shown in FIG. This product can be used as an index indicating the possibility that a phenomenon can occur. In the above equations 44 to 47, n: the number of the influencing factors m: the number of the influencing factors of interest t: a function between the magnitude of the influencing factors and the degree of the phenomenon t _R : each influencing factor takes a reference value The function between the magnitude of the influencing factor and the degree of the phenomenon at the time f function: the degree of the phenomenon in which the magnitude of the degree of each influencing factor is a variable X _i : the magnitude of the degree of the influencing factor i X _iR : the influencing factor i The magnitude of the reference degree θ: Influence factor function C: Constant

The features of the present invention are listed below. (1). Knowing the degree of various influencing factors on the phenomena of the equipment component materials, in the method of evaluating the reliability of the properties of the equipment components to evaluate the reliability of the properties of the equipment materials,
For each of the various influencing factors, focusing on an arbitrary influencing factor, keeping the degree of the other influencing factors constant, obtaining a first function between the magnitude of the influencing factor of interest and the degree of the phenomenon, Determine the reference level of the influencing factors, obtain a second function of the degree of the phenomenon when the various influencing factors take the reference value, calculate the ratio between the first function and the second function, and And a product of the function of the subdivision index of each of the influencing factors is multiplied by a correction coefficient to obtain an index representing the possibility that the phenomenon can occur. .

(2). A guideline and specifications for designing, manufacturing, preventive maintenance, inspection, and the like of the device are provided by taking into account an index indicating a possibility that the phenomenon obtained in the above (1) may occur.

(3). In the above (1), when multiplying by the correction coefficient to obtain an index indicating the possibility that the phenomenon can occur, the degree of the influencing factor is given by the Monte Carlo method and substituted into the correction coefficient. It is characterized by finding a possible frequency distribution.

(4). In the above (1) to (3), the first function is represented by any one of a Taylor expansion function, a function that can be approximated to the Taylor expansion, and a step function, and t _i = g _i (X _i ) (expression) 40) A function of the degree of the phenomenon when each influencing factor takes a reference value is obtained, and t _iR = g _iR (X _iR ) (Equation 41) The ratio of these functions is obtained, and the function of the subdivision index of the focused influencing factor is obtained. F _i = g _i (X _i ) / g _iR (X _iR ) (Equation 42) = F _i (X _i , X _iR ) (Equation 43) , A correction coefficient that is a function of the influencing factor is obtained by Taylor expansion, and the two are multiplied by each other to obtain an index indicating the possibility that a phenomenon may occur.

(5). In a method of evaluating the reliability of the characteristics of the component materials, which evaluates the reliability of the characteristics of the component materials by knowing the degrees of the various influencing factors on the phenomena of the component materials, the n of the various influencing factors may be determined for each Focusing on at least one or more m different influencing factors among the influencing factors, the degree of the other influencing factors is kept constant, and the first function between the magnitude of the noted influencing factors and the degree of the phenomenon is defined as It is expressed as any one of a Taylor expansion, a function that can be approximated to the Taylor expansion, and a step function with various influencing factor variables of various influencing factors, and t _ij … _ij = f _ij … _k (X _i , X _j …, X _k ) (Equation 44) Next, the degree of reference of each influential factor is determined, and a function value of the degree of the phenomenon when each influential factor takes a reference value is obtained. t _{ij... kR} = f _ij ... _kR (X _iR , X _jR ..., X _kR ) (Equation 45) The ratio F of the function of the operator is obtained. _{F ij ... k = t ij ...} k / t ij ... kR = f ij ... k (X i, X j ..., X k) / f ij ... kR (X iR, X jR ..., X kR) = F ij ... _k (X _i , X _j ,..., X _iR , X _jR ..., X _kR ) (Equation 46) And multiplying the two to obtain a logarithm as shown in (Equation 47) in FIG. 20, and using this product as an index indicating the possibility that a phenomenon may occur. In the above equations 44 to 47, n: the number of each influential factor m: the number of the influential factors of interest t: a function between the magnitude of the influential factor and the degree of the phenomenon t _R : when each of the influential factors takes a reference value, Function between magnitude of influencing factor and degree of phenomenon f function: degree of phenomenon in which magnitude of degree of each influencing factor is a variable X _i =: magnitude of degree of influencing factor i X _iR =: magnitude of influencing factor i The magnitude of the standard degree θ: function of the influencing factor C: constant

(6). In the above (1) to (5), the target value of the index is set by applying the method of the present invention to the damage data of a laboratory or an actual machine to obtain the correlation between the index and the degree of the phenomenon or the life. The correlation index is obtained by giving the degree of the allowable limit phenomenon and the lifetime for ensuring reliability to obtain an index of the limit.

(7). In the above (1) to (6), the product itself of the function between the magnitude of the focused influence factor and the degree of the phenomenon is used as an index indicating the possibility that the phenomenon can occur.

(8). In the above (1) to (7), the degree of the influence factor is the probability distribution or the average value of the probability distribution, while the degree of the phenomenon is the average value, the probability distribution, or the transition probability distribution.

(9). In the above (1) to (8), the phenomena are stress corrosion cracking, crack growth, erosion, general corrosion, pitting corrosion, wear, fatigue, corrosion fatigue, weld cracking, and their life phenomena. , Size of component materials, chemical components, mechanical strength and hardness of materials, stress acting on component materials, thermal stress, strain, residual stress, stress concentration coefficient, relaxation, microstructure of component materials Features include the state size of metallurgical knowledge such as crystal grain size and precipitates, heat history, welding conditions, heat input, the position of the heat affected zone, material surface processing state, oxide scale state amount, environmental conditions such as temperature, Oxygen concentration, hydrogen peroxide, hydrogen, nitrogen,
Nitric oxide, conductivity, PH, gap, chemical species, amount of radiation,
It is characterized in that it is used as a parameter of the use history of the device.

[0045]

As described above, according to the present invention, it is possible to quantitatively grasp the degree of the characteristics of each part of the device constituting material. Therefore, it is possible to take measures against accidents such as damage at the design stage of a new plant and as preventive maintenance of an existing plant. The present invention is extremely effective especially when high reliability is required as in a nuclear reactor plant.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a relationship between a degree of an influence factor and a damage life.

FIG. 2 is a characteristic diagram showing a relationship between a degree of an influence factor and a damage life ratio.

FIG. 3 is a diagram showing an equation of (Equation 6).

FIG. 4 is a characteristic diagram showing a relationship between a stress ratio S and log ₁₀ F.

FIG. 5 is a characteristic diagram showing a relationship between an influence of stress, a carbon content in stainless steel, and a material life time.

FIG. 6 is a characteristic diagram showing the relationship between the influence of stress, the carbon content in the Inconel material, and the material life time.

FIG. 7 shows a subdivision index F of carbon content in the case of stainless steel.
₁ is a flow chart for obtaining a subdivision index F ₃ = for low-temperature sensitization and a subdivision index F ₄ for stress relief annealing treatment.

FIG. 8 is a flow chart for obtaining a stress subdivision index F ₅ in the case of stainless steel.

FIG. 9: Subdivision index F of environmental effects in the case of stainless steel
₆ is a flow chart for obtaining the subdivided index F ₇ and F index gap.

FIG. 10 is a characteristic diagram showing a relationship between a stress ratio S and log ₁₀ F.

FIG. 11: Stress subdivision index F _{5 for} stainless steel
It is a flow chart that seeks.

FIG. 12 is a flowchart for obtaining a subdivision index F ₂ of the stabilization parameter N, a subdivision index F ₃ relating to low-temperature sensitization, and a subdivision index F ₄ of the stress relief annealing treatment in the case of an Inconel material.

FIG. 13 shows the stress subdivision index F _{5 in} the case of Inconel material.
It is a flow chart that seeks.

[14] subdividing index F ₆ environmental effects of the Inconel material, a flow chart for obtaining the subdivided index F ₇ and F index gap.

15 is a characteristic diagram showing the relationship of the stabilization parameters and subdivided index F _2.

FIG. 16 is a characteristic diagram showing a relationship between a stabilization parameter and a subdivision index F ₂ .

FIG. 17 is a characteristic diagram showing the presence or absence of stress corrosion cracking.

FIG. 18 is a life analysis characteristic diagram of stress corrosion cracking.

FIG. 19 is a characteristic diagram showing a relationship between a stress corrosion cracking (SCC) initiation time and an F index.

FIG. 20 is a diagram illustrating an equation of (Equation 47).

[Explanation of symbols]

t _i Lifetime g _i Function of _i- influencing factor i Xi Size of influencing factor i t _iR Lifetime of reference life system i Function of _iR- influencing factor i X Size of influencing factor i that constitutes _iR standard life system F _i Refinement index F ₁ Refinement index of carbon content (stainless steel) F ₂ Refinement index of stabilization parameter N (Inconel material) F ₃ Refinement index of low-temperature sensitization F ₄ Refinement index of stress relief annealing process F ₅ subdivided index of the subdivided index F ₆ environmental effects of stress

Continued on the front page (72) Inventor Takenori Shindo 6-9 Takara-cho, Kure City, Hiroshima Prefecture Inside the Kure Plant, Babkotsuk Hitachi Ltd. (72) Inventor Takashi Saito 3-1-1 Sachimachi, Hitachi City, Hitachi, Ibaraki Hitachi, Ltd. Hitachi Works, Ltd. (72) Inventor Shigeo Hattori 3-1-1, Sachimachi, Hitachi, Ibaraki Prefecture Hitachi Works, Ltd. Hitachi Works (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 33/20 G01N 17/00 G01N 37/00 G21C 17/003

Claims (4)

(57) [Claims] 1. A method for evaluating the reliability of characteristics of an equipment component material, which evaluates the reliability of the properties of the equipment component material by knowing the degree of various factors affecting the phenomenon of the equipment component material. For each of them, paying attention to any influential factors, keeping the degree of other influential factors constant, finding the first function between the magnitude of the influential factors of interest and the degree of phenomenon, The degree is determined, a second function of the degree of the phenomenon when the various influencing factors take the reference value is calculated, and the ratio between the first function and the second function is calculated to subdivide the focused influencing factor. Function of the component index, and then multiplying the product of the function of the subdivision index of each of the influencing factors by a correction coefficient to obtain an index indicating the possibility that the phenomenon can occur. Evaluation method of reliability. 2. The method according to claim 1, wherein when the correction coefficient is multiplied to obtain an index indicating the possibility that the phenomenon may occur, a degree of an influencing factor is given by a Monte Carlo method and substituted into the correction coefficient. And calculating a frequency distribution in which the phenomenon can occur. 3. The method according to claim 1, wherein
Wherein the first function is represented by any one of a Taylor expansion function, a function that can be approximated to the Taylor expansion, and a step function, and wherein the correction coefficient is obtained by the Taylor expansion. Sex evaluation method. 4. The method according to claim 1, wherein the phenomenon of the component material is stress corrosion cracking.